When someone chooses to start a diet, to quit smoking, or to enter an alcohol treatment program, they are showing that their preferences have changed. This project investigates the neural mechanisms underlying changes in preference. The focus is specifically on preferences for immediate versus delayed rewards, since exaggerated discounting of delayed rewards is a central process in many addictions. Previous research has shown that neural activity in two specific regions-medial prefrontal cortex and striatum-encodes the subjective value of immediate and delayed rewards during decisions. The proposed research will test whether shifts in preference are due to shifts in these neural value signals. This hypothesis will be tested for three kinds of preference changes: momentary changes due to contextual biases in decision-making (Aim 1); long-term changes due to explicit education and the use of self-control (Aim 2); and changes due to social learning (Aim 3). In each domain, manipulations will be designed to reduce myopic choices of smaller, immediate rewards and to enhance preferences for larger, delayed rewards. Functional neuroimaging will be used to identify what brain regions are engaged by these manipulations, and individuals with focal brain damage will be studied to test what brain regions are necessary for these manipulations to succeed. Since many addictions are characterized by frontal dysfunction, the studies of frontal lesions in particular will inform how these manipulations could work in addiction, and set the groundwork for future studies in addicted populations.